*B16* PRE-LEAVING CERTIFICATE EXAMINATION, 2011 PHYSICS ORDINARY LEVEL TIME: 3 HOURS Answer three questions from section A and five questions from section B. Page 1 of 10
SECTION A (120 marks) Answer three questions from this section. Each question carries 40 marks. 1. A student performed an experiment to verify Boyle s law. The student measured and recorded values for the volume of a gas for a range of different values of pressure. The table below shows the data recorded by the student. Pressure / kpa 100 125 200 250 500 1000 Volume / cm 3 10 8 5 4 2 1 1 Volume /cm -3 0.1 (i) Draw and label a diagram of the apparatus that was used in this experiment. (12) 1 (ii) Fill in the bottom row of the above table which will give the values for Volume. (5) 1 (iii) Plot a graph on graph paper with pressure on the y-axis and Volume on the x-axis. (12) (iv) How does the graph verify Boyle s law. (6) (v) Give one precaution that should be taken to improve the accuracy of the experiment. (5) 2. An experiment was carried out by a student to measure the speed of sound in air. A hollow glass tube was inserted into a large graduated cylinder of water. Different tuning forks were sounded one by one and they were held over the open end of the glass tube. This open end of the tube protruded above the water level. The tube was raised out of the water until resonance was detected. (i) Draw and label a diagram of the experimental arrangement. (12) (ii) How did the student detect the resonance. (6) (iii) How did the student measure the wavelength of the sound when resonance occurred. (6) (iv) How did the student find the value of the frequency when resonance occurred. (6) (v) (vi) When the frequency value was 256 Hz the student recorded a wavelength value of 1.33 m. Using this pair of values calculate the value of the speed of sound in air. (6) Give one precaution that the student might take to improve the accuracy of the experiment. (4) (c = f λ) Page 2 of 10
3. A student performed an experiment with the purpose of verifying Snell s law and at the same time to measure the refractive index of a glass block. The student arranged for a beam of light to fall on and pass through a glass block. The following data were recorded. Angle of incidence i 20 0 30 0 40 0 50 0 60 0 70 0 Angle of refraction r 13 0 19 0 25 0 31 0 35 0 39 0 sin i sin r sin i / sin r (i) Draw and label a diagram of the experimental arrangement. (12) (ii) (iii) Fill in the above table completely and find an average value for the refractive index of the glass. (12) Using the above data plot a graph with sin i on the y-axis and with sin r on the x-axis. (12) (iv) Explain how the graph verifies Snell s law. (4) (n = sin i / sin r) 4. An experiment was undertaken by a student to investigate the variation of current with potential difference for a copper sulphate solution. The student used a 6 V battery, an ammeter, a voltmeter, a rheostat (variable resistor), copper electrodes, several connecting wires and a beaker of copper sulphate solution. The value of potential difference (voltage) was measured along with the corresponding value of current. The rheostat was adjusted and the voltage and current were again recorded. The data is shown in the table below. Potential difference / V 0 1 2 3 4 5 Current / V 0 0.4 0.8 1.2 1.6 2.0 (i) Draw and label a diagram of the experimental arrangement. (12) (ii) Plot a graph with potential difference on the y-axis and current on the x-axis. (12) (iii) (iv) (v) What conclusion can you draw from the graph about the relationship between the current and the potential difference for the copper sulphate solution. (4) What would you observe in the experiment if the ammeter was placed where the voltmeter should be and the voltmeter was placed where the ammeter should be. (6) Using just one pair of values from the above table of data calculate a value for the resistance of the copper sulphate solution. (6) (R = V / I) Page 3 of 10
SECTION B (280 marks) Answer five questions from this section. Each question carries 56 marks. 5. Answer any eight of the following parts (a), (b), (c), etc. (a) (b) (c) (d) Calculate the work done when a force of 5 N moves an object 2 m in the same direction as the force. (7) A particle starting from rest is given an acceleration of 5 m s 2 for 6 seconds. Calculate the value of the final speed. (7) (v = u + at) A fish swimming in a tank of water appears nearer to the surface than it really is when viewed from above the water. What is the cause of this? (7) Draw a diagram to show what happens to a beam of white light when it is passed through a prism. (7) (e) What is the purpose of a diode in an electrical circuit? (7) (f) A plastic rod was rubbed with a cloth and the rod gained electrons from the cloth. What type of charge does the rod now have? (7) (g) Name any two of the three methods of heat transfer. (7) (h) A heat pump transfers heat energy from a cold region to a warmer region. Give an example of a heat pump you would find in the kitchen of most homes. (7) (i) Name the scientist who discovered X-rays. (7) (j) At the moment electricity is generated in nuclear power stations using nuclear fission. Name the radioactive material that is used as a fuel in the nuclear reactor. (7) Page 4 of 10
6. Weight is a vector quantity and mass is a scalar quantity. (i) Give one other difference between weight and mass. (6) (ii) State clearly the difference between a vector quantity and a scalar quantity. (6) (iii) State Newton s law of universal gravitation. (6) (iv) Calculate the value of the acceleration due to gravity on the surface of the earth given that the radius of the earth is 6.4 10 6 m, the mass of the earth is 6 10 24 kg and the universal gravitational constant is 6.7 10 11 N m 2 kg 2. (12) (v) What happens to the value of the acceleration due to gravity as you move away from the surface of the earth? (6) (vi) What would you need to do to experience the sensation of zero gravity? (5) (vii) A team of scientists were examining the values of the acceleration due to gravity on different planets. The values were compared to the values here on earth. What would be the difference between the acceleration due to gravity: (a) (b) if a planet had the same radius as the earth but had twice the mass of the earth. if a planet had the same mass as the earth but had twice the radius of the earth. (15) (g = GM / R 2 ) 7. What is the difference between a longitudinal wave and a transverse wave. Give an example of each. (12) Outline a laboratory demonstration experiment to: (i) show that sound needs a medium in which to travel (ii) show that sound is a wave. (18) An ambulance is approaching a person and the siren is emitting a sound of a particular frequency. As the ambulance passes by the person and moves away from the person the sound appears different. (a) What difference in the frequency of the sound will be noticed. (7) (b) What would be the difference in the wavelength of the sound. (7) (c) What is the name of this effect. (6) (d) Give one everyday use of this effect. (6) Page 5 of 10
8. (a) State the laws of reflection. (6) Draw a ray diagram the show the formation of an image in a convex mirror. (9) Give one everyday use for a convex mirror. (3) An object is placed a distance of 12 cm from a concave mirror of focal length 8 cm. Calculate the position of the image. If the object is 2 cm in size what is the size of the image. (10) (b) Draw a ray diagram to show the formation of an image in a diverging lens. (9) What is the type of lens found in the human eye? (6) The lens is flexible and can have different values of focal length. Why is this? (7) What type of lens is used to correct short-sightedness? (6) ( 1 u + 1 1 image size v = magnification = f object size = v u ) 9. What is an electric current? (6) Name the three effects of an electric current and give an everyday example of the use of each of the three effects. (18) The voltage in Irish homes is 230 V. A person buys a microwave oven that is rated 900 Watt. Calculate the current that is normally used by the oven. (6) If the plug of the microwave oven had a 3A fuse what would you notice when the oven is switched on at full power for the first time. Give a reason for your answer (9) Energy is measured in the joule. Power companies tend to use the kilowatt-hour as their unit of energy. Why is this? (3) How many joules of energy is there in 1 kilowatt-hour. (6) If the cost of 1 kilowatt-hour is 15 cent, calculate the cost of using a 500 W bulb for a full day. (8) ( P = V I ) Page 6 of 10
10. What is the difference between photoelectric emission and thermionic emission? (12) Give two properties of electrons. (6) Electrons were originally known as cathode rays. Name the Irish scientist who changed the name to the electron. (6) Electric field Electron gun Coil Electron beam Spot Anodes Coil Phosphor-coated screen In the cathode ray tube shown above: (i) Why do the electrons travel towards the anodes? (6) (ii) Why are the electrons deflected. (6) (iii) How could you deflect the electron beam downwards. (6) (iv) Why does a spot of light appear on the screen? (7) (v) Name two instruments in everyday life that are based on the cathode ray tube. (7) Page 7 of 10
11. Read the following passage and answer the accompanying questions. Electrical transformers are used to transform voltage from one level to another, usually from a higher voltage to a lower voltage. They do this by applying the principle of electromagnetic induction between coils to convert voltage and/or current levels. Electric motors use electrical energy to produce mechanical energy typically through the interaction of magnetic fields and current carrying conductors (a) What is electromagnetic induction? (7) (b) What material is the transformer core made of? (7) (c) Transformers work with a.c but not with d.c Explain why this is so. (7) (d) Give an example of where you would use a transformer in everyday life. (7) (e) Explain the difference between a step-up transformer and a step-down transformer. (7) (f) The input voltage is 230 V and the primary coil has 1,000 turns. If the secondary coil has 200 turns calculate the value of the output voltage. (7) (g) What happens when a current carrying conductor is placed in a magnetic field? (7) (h) Calculate the force on a conductor of length 50 cm carrying a current of 2 A when placed in a magnetic field of magnetic flux density 3 T. (7) ( V i / V 0 = N p / N s ) ( F = B I l ) Page 8 of 10
12. Answer any two of the following parts (a), (b), (c), (d). (a) Define the moment of a force. (6) The uniform metre stick below (centre of gravity at the 50 cm mark) has a weight of 1 N. 8 N 8 N 20 25 56.58 80 10 N 1 N 5 N (i) Calculate the total upward force on the metre stick. (3) (ii) Calculate the total downward force on the metre stick. (3) (iii) (iv) Calculate the moment of the upward forces about an axis through the 0 cm mark on the metre stick. (6) Calculate the moment of the downward forces about an axis through the 0 cm mark on the metre stick. (6) (v) Is the metre stick in equilibrium? (4) (b) What is the difference between heat and temperature. (6) What are the units used for heat and what are the units used for temperature. (6) A thermometric property is a physical property that changes measurably with temperature. Give two examples of a thermometric property. (6) What is the difference between latent heat of fusion and latent heat of vaporisation? (6) Humans perspire when their body temperature rises. What is the purpose of this? (4) (c) Define capacitance. (6) Name two everyday uses of capacitors. (6) Calculate the capacitance of a parallel plate capacitor if the common area of the plates is 0.1 m 2 and the plates are a distance of 2 mm apart. Let the permittivity of the medium between the plates be 5 10 12 F m 1. (12) If the voltage across the above capacitor is 6 V calculate the charge stored on the capacitor. (4) ( C = ɛ A / d, C = Q / V ) Page 9 of 10
(d) Give two properties each for α, β and γ radiation. (12) Name an instrument that can be used to measure levels of radioactivity. (3) The half-life of a radioactive material is given as 4 hours. What is meant by this? (6) Give two everyday used for radioactive materials. (7) Page 10 of 10